Process for the polymerization of 1,2-dimethoxyethylene

ABSTRACT

A PROCESS FOR THE POLYMERIZATION OF 1,2-DIMETHOXYETHYLENE USING HALOGEN CONTAINING ORGANO ALUMINUM COMPOUNDS AS POLYMER INITIATORS IS DISCLOSED. THE PRESENT PROCESS ENABLES THE PREPARATION OF POLYDIMETHOXYETHYLENES HAVING MOLECULAR WEIGHTS IN EXCESS OF 60,000.

United States Patent 3,792,030 PROCESS FOR THE POLYMERIZATION 0F1,2-DIMETHOXYETHYLENE Norbert Vollkammer, Troisdorf, and Wilhelm Vogt,

Cologne, Germany, assignors to Dynamit Nobel AG,

Troisdorf, Germany No Drawing. Filed Dec. 13, 1971, Ser. No. 207,648

Claims priority, application Germany, Dec. 18, 1970, P 20 62 400.4 Int.Cl. C081? 3/34 US. Cl. 260-911 R 8 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the polymerization of 1,2-dimethoxyethylene using halogencontaining organo aluminum compounds as polymer initiators is disclosed.The present process enables the preparation of polydimethoxyethyleneshaving molecular weights in excess of 60,000.

BACKGROUND OF THE INVENTION It is known that 1,2-dimethoxyethylene(DMOE,) can be polymerized with BF, etherate according to a cationicmechanism (S. S. Skorochodov, V. V. Stepanov; Vyso- 'komol. Soedin, Ser.B 1969, 11 362).

Although DMOE, being a 1,3-disubstituted ethylene, has a lowerreactivity in polymerization than, for example the likewise catiom'callypolymerizable alkyl vinyl ethers, the polymerization takes place veryenergetically in substance, even at low temperature with intensiveexternal cooling, and under these conditions, when BF etherate is usedas the initiator, it results in products of low molecular weight havinga brownish black discoloration. The polymerization of DMOE has thereforebeen performed hitherto at temperatures below 0 0., preferably at -78C., in the presence of an organic solvent for both the monomer and thepolymer, such as toluene, dialkyl ethers or methylene chloride. Anotherdisadvantage of the BE, etherate that is used is that the results(polymerization speeds, transformations and molecular weights) arereproducible only with great difliculty. Like the other FriedeLCraftscatalysts, this catalyst has the disadvantage that the polymerization isoften very diflicult to start, even when great concentrations ofinitiator are used. It is for this reason that BF, etherateconcentrations of up to 12 molepercent, with reference to the monomer,are used according to the literature. As a result of the high catalystconcentration, the progress of the polymerization, once it has beenstarted, may be very violet and result in greatly discolored products.The polydimethoxyethylenes thus obtained are of low molecular weight:according to the literature molecular weights no higher than 30,000 areobtained. In spite of the high initiator concentration transformationsbarely higher than 80% are achieved. When the BE, etherate concentrationis lower (3.6 molepercent), the polymerization speed is very low: in a50% solution (methylene chloride) a transformation of only 41% isachieved in 48 hours. The polydimethoxyethylenes obtained under theseconditions are described on the basis of X-ray analysis as amorphous.

The above disadvantages are avoided when the initiators of the inventionas well as the polymerization process of the invention are used.

DESCRIPTION OF THE INVENTION The subject of the invention is a processfor the polymerization of 1,2-dimethoxyethylene, which is characterizedby the fact that halogen-containing organic aluminum compounds of thesum formula Al(R) X are used as polymerization initiators, R being asaturated aliphatic, branched or unbranched hydrocarbon radical with 1m6 carbon atoms or phenyl, -X is a halogen such as chlorine or bromine,m and 11 represent the numbers 1, 1.5 or 2, and the sum of m and n isthe number 3. In addition, mixtures of these organo aluminum compoundssuch as dimeric organo aluminum sesqui-halides can also be used.

Examples of preferred initiators are: dimethylaluminum chloride,dimethylaluminum bromide, diethylaluminum chloride, diethylaluminumbromide, diisobutylaluminum chloride, methylaluminum sesquichloride,ethylaluminum dichloride, ethylaluminum sesquichloride, phenylaluminumdichloride and diphenylaluminum chloride.

The initiators of the invention have a number of advantages over BF,etherate: ,the polymerization results are very well reproducible asregards transformations and molecular weights. Virtualy quantitativetransformations can be obtained, as well as previously unknown highmolecular weights.

Still another subject of the invention, therefore, is polymers of1,2-dimethoxyethylene with the repetitive and with molecular weights inexcess of 60,000.

The course of the polymerization with the use of the organic aluminumcompounds is very controllable, because the speed of polymerization isonly slightly dependent upon the initiator concentration and thetemperature. Whereas with BF, etherate controlled polymerization ispossible only in dilute solutions, it is possible, when the organicaluminum compounds of the invention are used, to polymerize in anorganic dispersion, which offers advantages as regards polymerizationspeed, molecular weights and especially the refinement of the polymersafter interruption of the polymerization.

It has been found that DMOE is very difficulty soluble in aliphatichydrocarbons in the temperature range -30 C. The monomer can thus bepolymerized in suspension to special advantage by the use of theorganometallic compounds, and low-boiling liquid hydrocar bons such aspropane or butane are preferred as suspension agents for the monomer. Inthis case the poly- DMOE is immediately produced in a rubber-like formand can easily be obtained after removal of the suspension agent byevaporation.

The ratio of the monomer to the suspension agent is best from 1:2 to1:3. If the ratio is substantially higher (say, 1:1), the polymerizationstill takes place under good control, but products of low molecularweight are formed and the transformation is not improved.

The quantity of the initiators advantageously amounts to between 0.1 and10 mole-percent, and it is preferably between 1 and 6 mole-percent withreference to the monomers.

The polymerization temperature can be between 0 and C., and it ispreferably between -30 and -60 C.

The most advantageous polymerization temperature is between -40 and 55C. In spite of the melting point .of the monomer (-90% cis-DMOE and15-10% trans- DMOE) of about 30 C., it is possible to keep the DMOEdispersed in liquid form at 50 C. until the initiator is added. Forsafetys sake (to prevent premature crystallization), a small amount(say, 2%) of trimethoxyethane can be added to lower the freezing point.The addition of trimethoxyethane does not have a negative influence onthe transformation and molecular weight. Temperatures substantiallylower than -60 C. can be used with only difficulty reproducible resultsbecause the danger exists that the monomer might crystallize out beforethe initiator is added and the polymerization has begun. Polymerizationtemperatures higher than '40 C. have a decided effect on the molecularweights of the products obtained; thus the selection ofthe temperatureoffers a simple way of controlling the molecular weight.

The polymerization speed and the final transformation are not greatlydependent upon the initiator concentration, but the molecular weightsare more greatly affected thereby. At an initiator concentration ofmole-percent with reference to the monomer the molecular weights attainthe highest values.

The polymerization time, under the polymerization conditions describedabove, is between 2 and 4 hours. It is best for the course of thepolymerization to be such that, at 50 C. in a propane or butanesuspension, most of the polymer (80%-85%) is obtained in 1 to 2 hours ofreaction time, and then, after the evaporation of the suspending agentat 45 and 0 C., respectively, the batch continues to be polymerized atthe latter temperature (virtually in substance) down to the final degreeof transformation. The polymerization is terminated by destroying thecatalyst by the addition of alcohol.

The DMOE monomer was obtained from trimethoxyethane by splitting offmethanol catalytically in the gaseous phase and consisted, on the basisof gas chromatography, of 85 to 90% cis-DMOE and to trans-DMOE.

The polydimethoxyethylenes obtainable by the invention are colorless, incontrast to the products prepared with BF 3 etherate.

The molecular weights (osmotic numerical average) amount to from 60,000to 350,000 and more. Polymers with molecular weights of 80,000 to270,000 are preferred for a number of applications.

As molecular weight comparisons of the numerical average values with theweight average values show, they have a narrow molecular weightdistribution.

As X-ray diagrams show, the polydimethoxyethylenes obtainable by theprocess of the invention have a definite crystallinity, the crystallinepercentage being about 10%. In contrast, the polymers obtained with BF;etherate are described in the literature as amorphous.

Furthermore, as shown by measurements of nuclear magnetic resonance,there are definite differences of tacticity in comparison with thepolydimethoxyethylenes obtained with BF etherate. While the percentageof isotactic sequences is the same in both polymerizations, thesyndiotactic sequences in the polydimethoxyethylenes prepared with theorganic aluminum compounds is greater, at the expense of theheterotactic sequences, than it is in a poly- DMOE obtained with BFetherate.

The polydimethoxyethylenes obtained with the organic aluminum initiatorsdisplay a substantial improvement in thermal stability of shapeaccording to Vicat. The Vivat temperature (DIN 53,460, in air) is morethan 30 C. higher than it is in a polydimethoxyethylene prepared with BFetherate.

The polymers prepared are soluble in water. It is possible to make theminto tear-resistant sheets, with the addition, if desired, ofplasticizers such as polyethylene glycol or polypropylene glycol, sothat bags can be made of them which are to dissolve in water.

The molecular weights of the polydimethoxyethylenes were determined bymembrane osmosis as well as by gel chromatography; otherwise themolecular weights were determined on the basis of the equation which hasbeen formulated for unfractionated polydimethoxyethylenes.

The viscosimetric measurements were performed in water at C. and at a.concentration of 0.01 g./ml.

' 4 The following examples are intended to further explain theinvention.

EXAMPLE 1 In a wide-necked reaction vessel with a 500 ml. capacity,provided with a stirrer, thermometer and gas inlet and outlet tubes, andexternally refrigerated to 50 C., 91.7 g. (100 ml.)=1.04 moles of1,2-dimethoxyethylene cis and 10% trans isomers) dried over sodiumhydroboride were placed after the air had been removed by displacementwith a current of dry nitrogen. Then, at 50 C., 250 ml. of dry propanewas condensed into the vessel and the monomer was dispersed in dropletform in the hydrocarbon by intense agitation. Then 6.24 g. (0.052 mole).of aluminum diethyl monochloride in the form of a 30 wt.-percentsolution in petroleum ether was added to the contents of the vessel. Theamount of initiator is S mole-percent with reference to the monomer. Thepolymerization starts immediately, manifesting itself in theprecipitation of a soft, plastic mass of polymer. The batch ispolymerized for 2 hours at 50 C.; then the suspension agent is removedby evaporation at -45 C. and the batch is further polymerized at thistemperature for an additional hour.

By the addition of 10 ml. of ethanol the catalyst is destroyed and thecolorless, rubber-like polydimethoxyethylene is freed under a vacuum ofresidual monomer and any adhering suspension agent, whereupon thepolymer becomes hard. It is refined by dissolving in water at roomtemperature and precipitation by heating the aqueous solution to 65 C.88.6 g. of polydimethoxyethylene are obtained; the transformation is96.6%. The polymer has a reduced specific viscosity in water of 472mL/g. and an osmotic molecular weight of 255,000.

A film cast from a methanol solution of the polymer displayed a decidedcrystallinity in the X-ray diffraction diagram, the crystallinity beingestimated at 10%.

A sheet of the material of Example 1 in a thickness of 0.18 mm. andhaving a moisture content of about 2% has a tensile strength of 500kp./cm. and an elongation at rupture of 4.8%.

On the other hand, no mechanically stable sheet could be produced at allfrom a product having a molecular weight of 35,000 which had beenprepared with BF -etherate on the basis of information given in theliterature (S. S. Skorochodov, loco citato).

EXAMPLES 2 AND 3 EXAMPLES 4, 5, 6 AND 7 In the same manner as in Example1, 91.7 g. ml.) =l.04 moles of DMOE were dispersed in each case in 250ml. of liquid propane at -50 C. and polymerized at 5 0 C. with varyingconcentrations of aluminum diethyl monochloride. The polymerization timetotaled 3 hours in all cases.

Initiator concentra- Polymer Transtor- Molecular tion, moleln matlon,71511.0 weight Example percent grams percent m1./g. (osmotic) A sheetprepared from the polydimethoxyethylene of Example 5 (molecular weight165,000) with 2% atmospheric moisture has a'tensile strengthof .400kp./cm. and an elongation at rupture of 2.5%.

The molecular weights of the polydimethoxyethylenes of Examples 4 and 7were also determined by gel permeation chromatography. The osmoticvalues of 140,000 and 100,000 compare with gel chromatography values of200,- 000 and 113,000, respectively, which indicates a narrow molecularweight distribution.

A plate pressed from the material of Example-4 prepared at 120 C. presstemperature and at a cooling rate of approximately 20 C. per minuteshows a decided crystallinity in the X-ray diffraction diagram(approximately crystallinity).

For a comparison of the tacticity and Vicat stability of shape of apolydimethoxyethylene obtained in accordance with the invention (productfrom Example 5 with a product prepared with BF etherate, apolydimethoxyethylene with a molecular weight of 35,000 was synthesizedin accordance with information given in the literature (S. S.Skorochodov, loc. cit.).

In the NMR spectrum (Varian A-60), the proton signals for syndiotacticsequences appear at 6:3.74 p.p.m., for isotactic sequences they appearat 6:330 p.p.m., and for heterotactic sequences they appear at 6:3.62p.p.m. Integration of the signals gives the following sequencedistribution:

B Fa etherate Al(C2Hs)z Initiator Isotactlc sequences, percent 20 20syndiotactic sequences, percent. 10 30 Heterotactic sequences, percent70 50 EXAMPLE 8 20 g. (0.23 mole) of DMOE was placed in a 250 ml.wide-necked reaction flask equipped with stirrer, thermometer and gasinlet and outlet tube, after displacement of the air by dry nitrogen,and then 50 ml. of butane was condensed into the flask at 30 C. Themonomer was distributed in droplet form into the suspension agent byintense agitation, and 1.38 g. (0.012 mole) of Al(C H Cl in petroleumether as diluent (30% solution) was added. The initiator concentrationamounted to 5 mole percent. After 3 hours the polymerization isinterrupted and the initiator destroyed by the addition of 5 ml. ofethanol. The suspension agent was removed by evaporation at roomtemperature and the polymer was freed of residual monomer and adheringsuspension agent. 16 g. of poly-DMOE was obtained; the transformationwas 80%. The reduced specific viscosity amounted to 156 ml./g., and themolecular weight was 95,000. A sheet of the material 0.28 mm. thick castfrom a methanol solution had a tensile strength of 125 kp./cm. and anelongation at rupture of 2%, at a moisture content of 2%.

6 Similar results were obtained by the use of equivalent amounts ofA1(CH Cl and Al(i-C H Cl instead of Al(C H Cl.

EXAMPLE 9 18 g. (0.21 mole) of DMOE was placed in a polymerizationvessel with a capacity of 250 ml., after removal of the air bydisplacement with dry nitrogen, and 50 ml. of propane was condensed intothe vessel at -50 C. The ratio of monomer to suspension agent was 1:2.5.1.33 g. (0.0105 mole) of aluminum monoethyl dichloride was added to thedispersed monomer and the batch was polymerized at 50 C. The initiatorconcentration, with reference to the monomer, amounted to 5 molepercent. The course of the polymerization is no different from that ofthe batches started with Al(C H Cl. After 2 hours the propane waevaporated away at 45 C., the batch was allowed to polymerize further atthis temperature for another hour, and the initiator was destroyed bythe addition of 2 ml. of ethanol. After the poly-DMOE primarily producedin rubber-like form was dried, 16.1 grams of a hard product was theresult. The transformation percentage was 88%. The polymer had a reducedspecific viscosity of 290 ml./ g. and a molecular weight of 163,000.

EXAMPLE 10 Using the same procedure and the same polymerizationconditions as in Example 9, aluminum sesquichloride (A1 (C H Cl is usedas the initiator in Example 10. Amount of initiator: 0.5 g. 18.2 g. ofpolydimethoxyethylene is obtained, which corresponds to a virtuallyquantitative transformation. The polymer has a reduced specificviscosity of 180; the molecular weight amounts to 108,000.

EXAMPLE 11 Using the procedure of Example 9, but polymerizing at -45 C.,phenylaluminium dichloride in an amount of 1.4 g. is used a theinitiator instead of aluminium monoethyl dichloride. Polymerizationprocess and resulting polymer were found corresponding as specified inExample 9.

What is claimed is:

1. A process of polymerizing 1,2-dimethoxyethylene which comprisescontacting 1,2-dimethoxyethylene at a temperature in the range of 0 toC. with an initiator in an amount between 0.1 and 10 mole percent basedupon said 1,2-dimethoxyethylene, which is of the group ofhalogen-containing organo aluminum compounds having the formula:

)m n wherein R is a saturated aliphatic radical of from 1 to 6 carbonatoms, or phenyl,

X is chlorine or bromine,

m and n are each 1, 1.5 or 2, the sum of m and n being 3.

2. The process of claim 1 in which the initiator is dimethylaluminumchloride, dimethylaluminum bromide, diethylaluminum chloride,diethylaluminum bromide, diisobutylalurninum chloride, methylaluminiumsesquichloride, ethylaluminum dichloride, ethylaluminum sesquichloride,phenyl aluminium dichloride or diphenylaluminium chloride.

3. The process of claim 1 in which the initiator is present in an amountof from about 1 to 6 mole percent and the polymerization is carried outat temperatures of from about 30 to 60 C.

4. The process of claim 3 in which the polymerization is carried out attemperatures of from about -40 to 55 C.

5. The process of claim 1 in which the polymerization takes place in asuspension of a liquid hydrocarbon.

6. The process of claim 5 in which the hydrocarbon is selected from thegroup consisting of propane, butane and mixtures thereof.

7 7. A water-soluble homopolymer dimethoxyethylene References Citedhaving the recurrent unit UNITED STATES PATENTS Haco 2,526,743 10/1950Gresham 260-91.1 R I 5 3,231,554 1/1966 Kern 26O--91 1 M and an osmoticaverage number molecular weight between HARRY W Pnmary Exammer about60,000 and 350,000, said polymer having a crystallinity of about 10%.

8. The polymers of claim 7 having a molecular weight 10 A of from about80,000 to 270,000. 1

mg I UNITED STATES PATENT-OFFICE v CERTIFICATE OFCORRECTION I Patent No. 3 ,792,030 Q mired Felguary 12 1974 '7 ln v e n to fl s) Nol rbeft \lollkommer and w il heln Vog}: I

It-is certified that error appears-1n the aboye-identified patent andthat said Ltte rs Patent ar e hercby correctadjs shown below:

"'5;6 10 should be "5.6 10' Signed and sealed this 24th day of September1974.

(SEAL) Attest: v k

MCCOY M} GIBSON JR. c; m sHALL DANN Atts'ting 0 fficer 'Cqmmi'ssionerof- Patents

